Pre-tightening device for safety belt retractor and safety belt retractor

Abstract

The invention relates to a pre-tensioning device for a seat belt retractor, a seat belt retractor and a seat belt device. The pre-tightening device comprises: a tube assembly (3) in which a set of mass bodies (3.4) is housed; a gas generator (3.2); and a drive wheel (2.2) coupled to the reel. The tube body has an extension (3.1. 3) on the outlet side, which extends around the drive wheel and is open towards the drive wheel, such that the drive wheel can be driven in rotation by the mass body in a first rotational direction, and thus the reel can be driven in rotation by the drive wheel in a webbing take-up direction. According to the invention, the tube body has a relief (3.1. 4) which forms a section of the guide path of the extension and which is designed such that, when the drive wheel exerts a pressure load on the relief by means of a mass in the outlet region, the relief can relieve the mass. The mass body can be brought into engagement with the drive wheel or can be disengaged from the drive wheel.

Description

Technical Field

[0001] The present application relates to the field of safety technologies, in particular to the field of vehicle safety technologies. More specifically, it relates to a pre-tensioning device for a seat belt retractor and a seat belt retractor including such a pre-tensioning device. Background Art

[0002] In modern vehicles, the seat belt device is an important part of the vehicle occupant restraint system. Especially in traffic accidents, the seat belt device can provide protection for vehicle occupants, avoiding injuries to the occupants or minimizing the injuries. With the continuous increase in the vehicle ownership, vehicle users have higher and higher requirements for the safety performance of the seat belt device.

[0003] In the case of traditional seat belt devices, there is a gap between the webbing and the occupant's body before a vehicle collision, and the webbing may not effectively fit the occupant's body. During a collision, the gap between the webbing and the occupant's body will delay the time when the seat belt device effectively plays a protective role and reduce the protection effect.

[0004] Patent document DE19512660A1 discloses a seat belt device which includes a pre-tensioning device that includes a certain number of mass bodies. In a collision event, the gas generator can be activated, and the gas generated by the gas generator drives the mass bodies. Then these mass bodies drive the drive wheel coupled to the spool, so that the spool rotates in the webbing retraction direction, thereby realizing the pre-tensioning function of the seat belt device.

[0005] When the pre-tensioning function of the seat belt retractor is activated, after the webbing is pre-tensioned, the force exerted by the occupant on the webbing can continue to increase, and from a certain moment, this force exceeds the pre-tensioning force, causing the spool to then rotate in the webbing pulling-out direction opposite to the webbing retraction direction. Under predetermined conditions, the main locking function of the seat belt retractor can be triggered, and the continued pulling-out of the webbing is prevented. When the seat belt retractor has a load-limiting function, when the force on the webbing exceeds a predetermined threshold, the load-limiting device comes into play to prevent the webbing from exerting an excessive binding force on the occupant's body and causing secondary injuries to the occupant. Summary of the Invention

[0006] In the research and development, the inventors of the present application have found that seat belt retractors with a pretensioning device in the prior art may experience operational failures, and have identified possible causes for such operational failures. In a state where the seat belt device is worn by a vehicle occupant, the drive wheel of the pretensioning device may have an uncertain angular position due to various factors, which may include, but are not limited to: different occupant body sizes; different seat belt wearing operations; manufacturing errors of the seat belt device. Additionally, due to collision energy, occupant body size, manufacturing errors, or other factors, the pretensioning device may have different pretensioning strokes when activated. The uncertain angular position of the drive wheel and the uncertain pretensioning stroke may result in, after the pretensioning function is achieved, when the drive wheel starts to rotate in the rotational direction opposite to the pretensioning phase, a mass body that was about to disengage or had disengaged from the drive wheel at the end of the pretensioning phase may be re-engaged with the drive wheel by the teeth of the drive wheel (also referred to as "secondary engagement"), and then be driven by the drive wheel into the tube body. When secondary engagement occurs, the force exerted by the drive wheel on the mass body will fluctuate with the relative position between the drive wheel and the mass body. In an adverse situation, this force will jam or even completely lock the drive wheel, such that the reel coupled to the drive wheel cannot rotate normally in the webbing payout direction, and the seat belt retractor malfunctions. In the case where the seat belt retractor has a load-limiting function, this load-limiting function is adversely affected by the jamming of the drive wheel, and even the load-limiting function may be completely lost.

[0007] The object of the present invention is to provide a pretensioning device for a seat belt retractor, a seat belt retractor including such a pretensioning device, and a seat belt device including such a seat belt retractor, wherein the pretensioning device, the seat belt retractor, and the seat belt device can have improved operational reliability and avoid jamming of the mass body and the drive wheel and the resulting operational failures when secondary engagement occurs.

[0008] A first aspect of the present invention proposes a pretensioning device for a seat belt retractor, the pretensioning device comprising:

[0009] a tube assembly having a tube body in which a set of mass bodies is accommodated;

[0010] a gas generator that can generate pressurized gas when activated to drive the set of mass bodies accommodated in the tube body;

[0011] a drive wheel configured to be coupled to a reel of the seat belt retractor for winding the webbing;

[0012] Wherein, the tube body has an extension portion on the outlet side, the extension portion surrounds the drive wheel and is open towards the drive wheel, such that a mass body entering the extension portion from the tube body when the gas generator is activated can engage with the drive wheel, so that the drive wheel can be driven to rotate by the mass body in a first rotation direction, and thus the reel can be driven to rotate by the drive wheel in the webbing retraction direction;

[0013] Wherein, the tube body has a relief portion in the extension portion in the outlet region where the mass body disengages from the drive wheel, the relief portion forms a section of the guiding path of the extension portion, and the relief portion is designed such that when the drive wheel rotates in a second rotation direction opposite to the first rotation direction after rotating in the first rotation direction, in the case where the drive wheel is applied with a pressure load by a mass body in the outlet region, the relief portion can avoid the mass body, so that the mass body can enter into engagement with the drive wheel or can disengage from the drive wheel.

[0014] In the case of such a pre-tensioning device, when secondary engagement occurs, in the case where an unfavorable angle of the drive wheel relative to the mass body may cause the drive wheel to be jammed by the mass body as in the prior art, the relief portion deforms under the pressure load of the mass body, so that the mass body can be smoothly placed into engagement with the drive wheel by the teeth of the drive wheel, or the mass body can disengage from the drive wheel, for example, enter a storage channel for the mass body, thus at least substantially eliminating the operating failure caused by the drive wheel being jammed by the mass body when secondary engagement occurs.

[0015] In some embodiments, the material of the relief portion may have a yield strength smaller than that of the material of the extension portion.

[0016] In some embodiments, the extension portion of the tube body may be made of steel.

[0017] In some embodiments, the tube body may be made of steel.

[0018] In some embodiments, the relief portion may be at least partially made of a light metal material such as aluminum, magnesium, aluminum alloy, magnesium alloy, and / or a plastic material.

[0019] In some embodiments, the relief portion may be entirely made of a plastic material. As a supplement, reinforcing materials such as carbon fiber or glass fiber may be added to the matrix of the plastic material.

[0020] In some embodiments, the relief portion may be an injection molded part.

[0021] In some embodiments, the relief portion may be integrally formed. Alternatively, the relief portion may be formed in multiple parts.

[0022] In some embodiments, the avoidance portion may be installed in the extension portion in a press-fit manner.

[0023] In some embodiments, the extension portion may have an opening, and the avoidance portion is installed in the opening.

[0024] In some embodiments, the avoidance portion may be installed in the opening in a press-fit manner. As an alternative or supplement, the avoidance portion may be fixed in the opening by fasteners such as screws, and / or fixed in the opening by welding or bonding.

[0025] In some embodiments, the opening may be an elongated opening extending in the longitudinal direction of the extension portion.

[0026] In some embodiments, the opening may be a square hole.

[0027] In some embodiments, the avoidance portion may include a base portion and a guiding surface connected to the base portion, and the base portion is received in the opening.

[0028] In some embodiments, the guiding surface may overlap with the opening edge region of the extension portion that defines the opening.

[0029] In some embodiments, the guiding surface may have at least one of the following features:

[0030] - Arc-shaped extension in cross-section;

[0031] - Extending beyond the base portion on both sides in cross-section;

[0032] - Straight extension in the central longitudinal section;

[0033] - Extending beyond the base portion on both sides in the central longitudinal section;

[0034] - Symmetrically formed with respect to the central longitudinal section;

[0035] - The edge on the inlet side has a transition inclined surface to the extension portion;

[0036] - The edge on the outlet side has a step to the extension portion.

[0037] In some embodiments, the base portion may respectively have a plurality of interference ribs on two opposite longitudinal side surfaces, and the interference ribs are squeezed by the opening edge region, so that the base portion is received in the opening in a press-fit manner.

[0038] In some embodiments, the gas generator may be installed on the end of the pipe body facing away from the extension portion.

[0039] In some embodiments, a piston assembly for pushing the set of mass bodies may be provided in the tube body when the gas generator is activated.

[0040] In some embodiments, a clutch may be provided in the tube body in front of the set of mass bodies, and the clutch is configured to hold the set of mass bodies in the tube body when the gas generator is not activated, and enter the extension part and engage with the drive wheel when the gas generator is activated, so that the mass bodies entering the extension part after the clutch have a definite angular position with respect to the drive wheel.

[0041] In some embodiments, the mass bodies may be made of a metallic material, in particular steel.

[0042] In some embodiments, the mass bodies may be spheres, ellipsoids or rollers.

[0043] In some embodiments, the set of mass bodies is identically constituted.

[0044] In some embodiments, the pre-tensioning device may include a guide for guiding the mass bodies away from the drive wheel in the exit area where the mass bodies are disengaged from the drive wheel.

[0045] In some embodiments, the relief portion may be surface-treated such that the surface of the relief portion forming the guide path section has a reduced surface roughness. As an alternative or in addition, the relief portion may have a friction-reducing coating, such as a Teflon coating or a molybdenum disulfide coating.

[0046] A second aspect of the present invention relates to a seat belt retractor, which includes a frame and a reel for winding a webbing, the reel being rotatably supported in the frame, wherein the seat belt retractor further includes a pre-tensioning device for a seat belt retractor according to any one of the embodiments of the present invention.

[0047] In some embodiments, a load-limiting device may be integrated in the reel.

[0048] In some embodiments, the reel may include a reel body, a spindle rotatably supported at one end of the reel body, and a load-limiting rod, the load-limiting rod being torsionally connected to the reel body at one end and torsionally connected to the spindle at the other end.

[0049] In some embodiments, the drive wheel may be arranged coaxially with the reel.

[0050] In some embodiments, the drive wheel may be torsionally interconnected with the reel.

[0051] In some embodiments, the seat belt retractor may include a cover plate that is fixed to one side plate of the frame, and the drive wheel is torsionally mounted between the cover plate and the side plate on an end section of the reel that extends from the side plate.

[0052] In some embodiments, the seat belt retractor may have a storage passage, wherein, when the gas generator is activated, a mass body disengaged from the drive wheel can enter the storage passage, and the storage passage is jointly defined by the cover plate and the side plate.

[0053] In some embodiments, the seat belt retractor may be configured for a vehicle, in particular a land vehicle, such as a motor vehicle, especially a passenger car. The vehicle may be driven by an internal combustion engine, a hybrid drive, or a pure electric drive.

[0054] In some embodiments, the seat belt retractor may be configured to be mounted to the vehicle body or a vehicle seat.

[0055] Other aspects of the present invention may relate to a seat belt device having the seat belt retractor; a vehicle seat provided with the seat belt device; and a vehicle provided with the seat belt device or the vehicle seat.

[0056] Herein, a "torsion-resistant connection" may mean that two connected components are substantially unable to rotate relative to each other, including, but not limited to, the following examples: 1) The two components are integrally formed and can thus rotate together. 2) The two components can rotate together through a connection structure, for example, the two components are connected by a spline connection, or by a non-circular hole and a shaft with a non-circular cross-section. For example, the two components may be fixedly connected to each other, or the two components may be non-rotatable relative to each other around the rotation axis but movable relative to each other along the rotation axis. 3) The two components are fixed to each other by a material-locking connection. For example, the two components are welded or bonded to each other. Combinations of various different connection techniques are also possible.

[0057] The above-mentioned technical features, the technical features to be mentioned below, and the technical features shown separately in the drawings can be arbitrarily combined with each other as long as the combined technical features are not mutually contradictory. All feasible feature combinations are the technical content clearly recorded herein. Any one of the sub-features included in the same statement can be independently applied without necessarily being applied together with other sub-features. BRIEF DESCRIPTION OF THE DRAWINGS

[0058] The present invention will be described in more detail below with reference to the accompanying drawings by means of exemplary embodiments. The accompanying drawings are briefly described as follows:

[0059] Figure 1 is an exploded perspective view of a seat belt retractor according to an embodiment of the present invention.

[0060] Figure 2 is Figure 1 a perspective view of a tube assembly of the seat belt retractor of

[0061] Figure 3 is Figure 2 a partially cut-away view of the tube assembly of

[0062] Figures 4A - 4C is a perspective view, a cross-sectional view, and a central longitudinal sectional view of an avoidance portion according to an embodiment of the present invention.

[0063] Figure 5 is Figure 1 an exploded perspective view of a spool and a drive wheel of the seat belt retractor of

[0064] Figure 6 is a perspective view of an embodiment of a clutch for a pretensioner.

[0065] Figure 7 is Figure 1 a perspective view of an end cap of the seat belt retractor of

[0066] Figures 8 - 11 is Figure 1 a partially cut-away front view of the seat belt retractor of , where the pretensioner is in different states. Detailed Embodiments

[0067] Now, multiple exemplary embodiments will be described more fully with reference to the accompanying drawings. It should be recognized that for the purposes of ease of illustration and understanding, elements that are not necessary for understanding the present invention may be omitted from the drawings. In the drawings, the same reference numerals may represent the same components or components with the same functions. Many specific details are set forth in the following description, such as examples of specific components, devices, and methods, to provide a thorough understanding of the embodiments of the present disclosure. It will be apparent to those skilled in the art that not all of these specific details need necessarily be employed. The exemplary embodiments should not be construed as restrictive.

[0068] Figure 1is an exploded perspective view of a seat belt retractor 100 according to an exemplary embodiment of the present invention. The seat belt retractor 100 includes a frame 1. The frame 1 is typically configured as a U-shaped frame, and the U-shaped frame may have two side plates 1.1 and 1.2. The seat belt retractor 100 can be mounted to a motor vehicle through the frame 1, for example, mounted to the body of the motor vehicle or the backrest of the vehicle seat. A reel 2 is rotatably supported in the frame 1. When the reel 2 rotates in the webbing retraction direction, the webbing of a seat belt device (not shown) can be wound around the reel 2. When the reel 2 rotates in the webbing pulling-out direction opposite to the webbing retraction direction, the webbing can be unwound from the reel 2. The reel 2 can be received in the holes of the two side plates 1.1 and 1.2 of the U-shaped frame 1. For example, the reel 2 can be rotatably supported in the hole of the side plate 1.1, and additionally, a toothed ring can be formed in the hole of the side plate 1.2, and a claw or tooth (not shown) of the main locking device can lock the reel 2 when meshing with the toothed ring. An end cap (not shown) can be provided beside the axial side of the side wall 1.2, and the main locking device can be received in the end cap. The reel 2 can be formed as a single piece or in multiple pieces. Typically, when the seat belt retractor 100 has a load-limiting function, the reel 2 can be formed in multiple pieces.

[0069] Please refer to Figure 5 , in the embodiment as Figure 5 shown, the seat belt retractor 100 has a load-limiting function. For this purpose, a load-limiting device is integrated in the reel 2. The reel 2 can include a reel body 2.1, and the reel body 2.1 can be configured as a hollow member, and a shaft head 2.4 is rotatably supported in the cavity of the reel body 2.1 at an open end of the reel body 2.1. The load-limiting device includes a load-limiting rod 2.3, and the load-limiting rod 2.3 is received in the cavity of the reel body 2.1, and the load-limiting rod 2.3 is torsionally connected to the reel body 2.1 at one end and torsionally connected to the shaft head 2.4 at the other end. As Figure 5 can be seen, the load-limiting rod 2.3 has splines at both ends, and the shaft head 2.4 also has splines in the hollow cylindrical portion extending from the disk body. Similarly, the reel body 2.1 has splines (not shown). The load-limiting rod 2.3 can fail when the torsional load exceeds a predetermined value, so that only a predetermined torsional load can be transmitted between the reel body 2.1 and the shaft head 2.4 by means of the load-limiting rod 2.3. The load-limiting function for seat belt retractors is known in various forms in the prior art.

[0070] The seatbelt retractor 100 includes a pretensioning device 10. In an exemplary application scenario, a motor vehicle is equipped with the seatbelt retractor 100. In the event of a collision, the pretensioning device 10 can be activated, thereby pretensioning a webbing (not shown), eliminating gaps between the webbing and the occupant's body, and providing improved safety protection for the vehicle occupants. The pretensioning device 10 can include a drive wheel 2.2. The drive wheel 2.2 is configured as a ball gear having transmission grooves 2.2.1 distributed around its circumference. The transmission grooves 2.2.1 are separated from each other by ribs 2.2.2 or teeth. A mass body 3.4 configured as a sphere can engage with the drive wheel 2.2 in the transmission grooves 2.2.1. When a metal sphere is used as the mass body 3.4, the transmission groove 2.2.1 can also be referred to as a "ball socket." The drive wheel 2.2 is configured to couple with the reel 2. In the embodiment shown, the drive wheel 2.2 is arranged coaxially with the reel body 2.1 of the reel 2 and is mounted in a rotationally fixed manner on an end section 2.5 of the reel body 2.1 facing away from the spindle head 2.4.

[0071] The prestressing device 10 further comprises a pipe assembly 3 which is fixedly connected to the frame 1 . Figure 2 is a perspective view of the tube assembly 3, and Figure 3 It is a partially cut-away view of the tube assembly 3. The tube assembly 3 includes a tube body 3.1. The tube body 3.1 may include a main body portion 3.1.1 having a complete peripheral wall and an extension portion 3.1.3 having an incomplete peripheral wall, wherein the extension portion 3.1.3 surrounds the drive wheel 2.2 and is open toward the drive wheel 2.2. The tube body 3.1 defines a channel 3.1.2, along which the mass bodies 3.4 can move one after another. These mass bodies 3.4 can be respectively constructed as metal spheres, in particular steel balls. In an alternative embodiment, an ellipsoid or a roller can also be used as the mass body. For simplicity, Figure 3 The mass body 3.4 housed in the tubular body 3.1 of the tubular assembly 3 is not depicted. A fixed gas generator 3.2 and a movable piston assembly 3.3 are mounted on one end of the tubular body 3.1.

[0072] For example, in the event of a vehicle collision, when the gas generator 3.2 is activated, the gas generator 3.2 generates pressurized gas that can push the piston assembly 3.3 and thereby push a set of mass bodies 3.4 downstream of the piston assembly 3.3 and a clutch 3.5 in front of the set of mass bodies 3.4. An exemplary embodiment of the clutch 3.5 will be described below with reference to Figure 6 Then, the mass body 3.4 which enters the extension portion 3.1.3 from the tube body 3.1 (more specifically the main portion 3.1.1 of the tube body 3.1) can engage with the drive wheel 2.2, so that the drive wheel 2.2 rotates in the first direction (in theFigure 1 Rotates counterclockwise (in the figure), and thus the reel 2 rotates in the webbing retraction direction to achieve the pre-tensioning function of the seat belt retractor 100.

[0073] Figure 6 Is a perspective view of an exemplary embodiment of the engagement device 3.5. The engagement device itself is known in various forms in the prior art. The exemplary engagement device 3.5 may include an engagement device body 3.5.1 and an engagement device bracket 3.5.2. The engagement device 3.5 may be configured to hold the set of mass bodies 3.4 in the tube body 3.1 when the gas generator 3.2 is not activated. For this purpose, the engagement device bracket may have a protrusion 33, and the tube body 3.1 may have a mounting hole 3.1.5, and the protrusion 33 may be held in the mounting hole 3.1.5. The engagement device 3.5 may be configured to disengage from the mounting hole 3.1.5 under the push of the piston assembly 3.3 when the gas generator 3.2 is activated, and then enter the extension 3.1.3 and engage with the drive wheel 2.2. In this case, the mass body 3.4 following the engagement device 3.5 has a determined angular position with respect to the drive wheel 2.2, and can enter into engagement with the drive wheel 2.2 well, avoiding working failures in an unfavorable relative angular position. The engagement device body 3.5.1 has a first sphere 21 and a second sphere 22. The first sphere 21 is a part of a complete sphere, and the complete sphere may be configured substantially the same as a mass body 3.4 made of a metal sphere. The second sphere 22 is a complete sphere, and may be configured substantially the same as a mass body 3.4 made of a metal sphere. When the pre-tensioning function is started, the relative angular position of the engagement device 3.5 and all the mass bodies 3.4 with respect to the drive groove 2.2.1 of the drive wheel 2.2 is adjusted by the specific contour of the first sphere 21 of the engagement device body 3.5.1, so that the second sphere 22 of the engagement device 3.5 and the subsequent mass bodies 3.4 can enter into engagement with the drive wheel 2.2 well. In the absence of the engagement device 3.5, the first mass body entering the extension 3.1.3 may be in an unfavorable angular position with respect to the drive wheel 2.2, and in this angular position, the first mass body hits a tooth of the drive wheel 2.2 head-on and cannot enter into a drive groove 2.2.1 of the drive wheel 2.2 well.

[0074] In the extension 3.1.3 of the tube body 3.1, in the exit area where the mass body 3.4 disengages from the drive wheel 2.2, the tube body 3.1 may have a relief portion 3.1.4. The relief portion 3.1.4 forms a section of the guiding path of the extension 3.1.3. In an exemplary embodiment of the relief portion 3.1.4, see Figure 2 、 Figure 3 and Figures 4A - 4C, the tube body 3.1 may have an opening 11 in the extension part 3.1.3, and the avoidance part 3.1.4 may be installed in the opening 11. To describe the opening 11, the avoidance part 3.1.4 installed in this opening 11 is not shown in Figure 2 . The opening 11 may be an elongated opening extending in the longitudinal direction of the extension part 3.1.3. The avoidance part 3.1.4 may be configured as an integral injection-molded part, which is installed in the opening 11 in a press-fit manner. The avoidance part 3.1.4 may include a base part 12 and a guiding surface 13 connected to the base part 12. The base part 12 is received in the opening 11. For example, the base part 12 may respectively have a plurality of interference ribs 14 on two opposite longitudinal side surfaces, and these interference ribs 14 are squeezed by the opening edge area, so that the base part 12 is received in the opening 11 in a press-fit manner. The guiding surface 13 overlaps with the opening edge area of the extension part 3.1.3 that defines the opening 11. As can be seen in the cross-sectional view as shown in Figure 4B , the guiding surface 13 extends arcuately in the cross-section, and the two opposite longitudinal edges of the guiding surface 13 respectively extend beyond the base part 12 and abut against the surface of the extension part 3.1.3 adjacent to the opening 11. As can be seen in the central longitudinal sectional view as shown in Figure 4C , the guiding surface 13 extends substantially linearly, the edge on the inlet side of the guiding surface 13 has a transition inclined surface 15 to the extension part 3.1.3, and the edge on the outlet side of the guiding surface 13 has a step 16 to the extension part 3.1.3. The transition inclined surface 15 may be advantageous so that the mass body 3.4 can smoothly reach the guiding surface 13 of the avoidance part 3.1.4 when it is pushed by the piston assembly 3.3 from the tube body 3.1. The step 16 may be advantageous so that the mass body 3.4 will not inadvertently return to the guiding surface 13 after passing over the avoidance part 3.1.4. The material of the avoidance part 3.1.4 may have a smaller yield strength than the material of the extension part 3.1.3. For example, the entire tube body 3.1 may be made of steel, while the avoidance part 3.1.4 may be made of plastic, or alternatively made of aluminum or magnesium.

[0075] Now, with reference to Figures 8 - 11 to illustrate the working principle of the pretensioning device according to an exemplary embodiment of the present invention. Figures 8 - 11 is Figure 1 a partially cut-away front view of the seat belt retractor 100 of

[0076] In the state as shown in Figure 8 , the pretensioning device 10 is not activated, and a set of mass bodies 3.4 are held in the main body part 3.1.1 of the tube body 3.1 by the engaging device 3.5.

[0077] In the state as shown in Figure 9In the state shown, the pre-tensioning device 10 has been activated and the pre-tensioning process is about to end. At this time, the clutch 3.5 and the two masses 3.4 are already in the storage channel 5.1, and one mass 3.4 (hereinafter referred to as the "special mass") is in contact with the guide 4 and is about to disengage from one of the drive slots 2.2.1 of the drive wheel 2.2. In the process from the state as shown in Figure 8 to the state as shown in Figure 9 , a set of masses 3.4 and the clutch 3.5 drive the drive wheel 2.2 under the push of the piston assembly 3.3, so that the drive wheel 2.2 rotates in the first rotation direction (counterclockwise in Figure 8 and Figure 9 ), and thus the reel 2 coupled to the drive wheel 2.2 rotates in the webbing retraction direction, the webbing is pre-tensioned, and the gap between the webbing and the occupant's body is eliminated.

[0078] In the state as shown in Figure 10 , immediately after the pre-tensioning process, the drive wheel 2.2 is about to rotate in the second rotation direction opposite to the first rotation direction (clockwise in Figure 10 ). At this time, the rib 2.2.2 or the tooth of the drive wheel 2.2 presses the special mass. The inventors of the present application have found that in the prior art, an unfavorable relative angular position of the special mass relative to the drive wheel 2.2 may cause the drive wheel 2.2 to be stuck or even completely jammed, so that the reel 2 coupled to the drive wheel 2.2 rotates poorly in the webbing pulling-out direction or even cannot rotate in the webbing pulling-out direction, which can lead to a malfunction of the seat belt retractor. In a vehicle collision event, such a malfunction can be detrimental to the safety protection of the occupant.

[0079] Now, by the measure of the present invention, when the special mass and the drive wheel 2.2 are re-engaged, when the tooth of the drive wheel 2.2 presses the special mass toward the avoidance portion 3.1.4, the avoidance portion 3.1.4 can avoid the special mass. Therefore, in one possibility, the special mass can smoothly enter into engagement with the corresponding drive slot 2.2.1 of the drive wheel 2.2, and this state is described in Figure 11 , at this time, the special mass has passed over the avoidance portion 3.1.4 in the reverse direction, that is, it has left the avoidance portion 3.1.4 from the edge of the entrance side or the transition slope 15 in the direction from the edge of the exit side of the avoidance portion 3.1.4 to the edge of the entrance side; in another possibility, the special mass can smoothly disengage from the drive wheel 2.2 and enter the storage channel 5.1.

[0080] In summary, the avoidance portion 3.1.4 is designed such that when the drive wheel 2.2 rotates in the second rotational direction after rotating in the first rotational direction immediately, and when the drive wheel 2.2 applies a pressure load to the avoidance portion 3.1.4 through a mass body 3.4 (special mass body) in the exit region, the avoidance portion 3.1.4 can undergo compressive deformation to avoid the mass body 3.4, enabling the mass body 3.4 to enter into engagement with the drive wheel 2.2 or to disengage from the drive wheel 2.2.

[0081] Advantageously, the avoidance portion 3.1.4 can be surface-treated such that the surface forming the guiding path section of the avoidance portion 3.1.4 has a reduced surface roughness. The avoidance portion 3.1.4 can have a lower coefficient of friction compared to the extension portion 3.1.3. As an alternative or supplement, the avoidance portion 3.1.4 can have a friction-reducing coating such as a Teflon coating or a molybdenum disulfide coating. On the one hand, the base material of the avoidance portion 3.1.4 can have a lower coefficient of friction compared to the extension portion 3.1.3, and the coefficient of friction is further reduced by the coating. Due to the smooth surface of the avoidance portion 3.1.4, when secondary engagement occurs, the mass body 3.4 can more easily enter into engagement with the drive wheel 2.2, or can more easily disengage from the drive wheel 2.2 and enter into the storage channel 5.1.

[0082] The pre-tensioning device 10 can further include a guide 4 that guides the mass body 3.4 away from the drive wheel 2.2 in the exit region where the mass body 3.4 disengages from the drive wheel 2.2. When a mass body 3.4 reaches the guide 4, the guiding portion 4.1 of the guide 4 separates the mass body 3.4 from the drive groove 2.2.1 of the drive wheel 2.2 and transfers it into the connecting channel 4.2, so that the mass body 3.4 reliably enters into the storage channel 5.1.

[0083] The seat belt retractor 100 can further include a cover plate 5, the cover plate 5 being fixed to the side plate 1.1 of the frame 1, and the drive wheel 2.2 being torsionally mounted between the cover plate 5 and the side plate 1.1 to the end section 2.5 of the reel 2 extending from the side plate 1.1. The storage channel 5.1 is jointly defined by the cover plate 5 and the side plate 1.1.

[0084] Note that the terminology used herein is for the purpose of describing particular aspects only and is not intended to limit the disclosure. As used herein, the singular forms "a" and "the one" shall include the plural forms unless the context clearly dictates otherwise. It will be understood that the terms "comprises" and "comprising," and other similar terms, when used in the application, specify the presence of the stated operations, elements, and / or components, without precluding the presence or addition of one or more other operations, elements, components, and / or combinations thereof. As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed items. In the description of the figures, like reference numerals always denote like elements.

[0085] The thickness of the elements in the figures may be exaggerated for clarity. It will also be understood that if an element is referred to as being on, coupled to, or connected to another element, then the one element may be formed, coupled to, or connected directly on the other element, or there may be one or more intervening elements between them. Conversely, if the phrases "directly on," "directly coupled to," and "directly connected to" are used herein, then there are no intervening elements. Other words used to describe the relationship between elements should be interpreted similarly, such as "between" and "directly between," "attached" and "directly attached," "adjacent" and "directly adjacent," etc.

[0086] Terms such as "top," "bottom," "above," "below," "upper," "lower," etc. are used herein to describe the relationship of one element, layer, or region to another element, layer, or region as shown in the figures. It will be understood that these terms should also encompass other orientations of the device in addition to the orientations described in the figures.

[0087] It will be understood that although terms such as "first," "second," etc. may be used herein to describe different elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another. Thus, a first element may be referred to as a second element without departing from the teachings of the inventive concept.

[0088] It is also contemplated that all of the exemplary embodiments disclosed herein may be combined with each other arbitrarily. Finally, it should be noted that the above embodiments are only for understanding the present invention and do not limit the protection scope of the present invention. For those skilled in the art, modifications can be made based on the above embodiments, and these modifications do not depart from the protection scope of the present invention.

Claims

1. A pre-tensioning device for a seat belt retractor, the pre-tensioning device comprising: a tube assembly (3), the tube assembly having a tube body (3.1) in which a set of mass bodies (3.4) is accommodated; a gas generator (3.2), the gas generator being capable of generating pressurized gas upon activation to drive the set of mass bodies accommodated in the tube body; and a drive wheel (2.2), the drive wheel being configured to be coupled to a reel (2) of the seat belt retractor for winding the webbing; wherein the tube body (3.1) has an extension (3.1.3) on the outlet side, the extension surrounding the drive wheel and being open towards the drive wheel, such that the mass bodies entering the extension from the tube body upon activation of the gas generator can engage with the drive wheel, so that the drive wheel can be driven to rotate by the mass bodies in a first rotational direction, and thus the reel can be driven to rotate by the drive wheel in the webbing winding direction; characterized in that the tube body (3.1) has a relief portion (3.1.4) in the extension (3.1.3) in an outlet region where the mass body (3.4) disengages from the drive wheel (2.2), the relief portion forming a section of the guiding path of the extension, the relief portion being designed such that when the drive wheel rotates in a second rotational direction opposite to the first rotational direction immediately after the rotation in the first rotational direction, in the case where the drive wheel applies a pressure load to the relief portion through a mass body in the outlet region, the relief portion can avoid the mass body, so that the mass body can enter into engagement with the drive wheel or can disengage from the drive wheel.

2. The pretensioning device for a seat belt retractor according to claim 1, characterized in that, The material of the relief portion (3.1.4) has a yield strength smaller than that of the material of the extension (3.1.3); and / or The tube body (3.1) is made of steel, and the relief portion (3.1.4) is at least partially made of a light metal material and / or a plastic material.

3. The pretensioning device for a seat belt retractor according to any one of claims 1 to 2, characterized in that, The extension (3.1.3) has an opening (11), and the relief portion (3.1.4) is installed in the opening; Preferably, the opening (11) is an elongated opening extending in the longitudinal direction of the extension (3.1.3); Preferably, the relief portion (3.1.4) has at least one of the following features: - being an injection molded part; - being integrally formed; - being installed in the opening in a press fit manner; Preferably, the relief portion (3.1.4) includes a base portion (12) and a guiding surface (13) connected to the base portion, the base portion being received in the opening (11), and the guiding surface overlapping with the opening edge region of the extension defining the opening; More preferably, the guiding surface (13) has at least one of the following features: - extending arcuately in cross-section; - extending beyond the base portion on both sides in cross-section; - extending linearly in the central longitudinal section; - extending beyond the base portion on both sides in the central longitudinal section; - being symmetrically formed with respect to the central longitudinal section; - the edge on the inlet side has a transition inclined surface (15) to the extension; - The edge on the outlet side has a step (16) leading to the said extension; Further preferably, the base (12) has a plurality of interference ribs (14) respectively on two opposite longitudinal side surfaces, and the interference ribs are squeezed by the opening edge area, so that the base is received in the opening in a press - fit manner.

4. The pretensioning device for a seat belt retractor according to any one of claims 1 to 3, characterized in that the gas generator (3.2) is installed on the end of the tube body (3.1) facing away from the said extension; and / or a piston assembly (3.3) for pushing the said set of mass bodies is provided in the tube body (3.1) when the gas generator is activated; and / or a clutch (3.5) is provided in the tube body (3.1) in front of the said set of mass bodies, and the clutch is configured to hold the said set of mass bodies in the tube body when the gas generator is not activated, and to enter the extension and engage with the drive wheel when the gas generator is activated, so that the mass bodies entering the extension after the clutch have a determined angular position with respect to the drive wheel.

5. The pretensioning device for a seat belt retractor according to any one of claims 1 to 4, characterized in that, The mass bodies are spheres, ellipsoids or rollers made of metallic material; and / or the pretensioning device (10) includes a guide (4) for guiding the mass bodies away from the drive wheel in the outlet area where the mass bodies are disengaged from the drive wheel; and / or the relief portion (3.1.4) is surface - treated so that the surface of the relief portion forming the guiding path section has a reduced surface roughness; and / or the relief portion (3.1.4) has a friction - reducing coating; and / or the drive wheel is arranged coaxially with the reel and is torsionally interconnected therewith.

6. A seat belt retractor, comprising a frame (1) and a reel (2) for winding a webbing, the reel being rotatably supported in the frame, characterized in that, The seat belt retractor further includes the pretensioning device for a seat belt retractor according to any one of claims 1 to 5.

7. The seat belt retractor according to claim 6, characterized in that, A load - limiting device is integrated in the reel; Preferably, the reel (2) includes a reel body (2.1), a hub (2.4) rotatably supported on one end of the reel body, and a load - limiting rod (2.3), and the load - limiting rod is torsionally connected to the reel body at one end and torsionally connected to the hub at the other end.

8. The seat belt retractor according to any one of claims 1 to 7, characterized in that, The seat belt retractor includes a cover plate (5), the cover plate is fixed to one side plate (1.1) of the frame, and the drive wheel (2.2) is torsionally mounted on the end section (2.5) of the reel extending from the side plate between the cover plate and the side plate. Preferably, the seat belt retractor has a storage channel (5.1), wherein when the gas generator is activated, the mass bodies disengaged from the drive wheel can enter the storage channel, and the storage channel is jointly defined by the cover plate and the side plate.

9. The seat belt retractor according to any one of claims 1 to 8, characterized in that, The seat belt retractor is configured for a motor vehicle.

10. A seat belt device, comprising a webbing, characterized in that, The seat belt device includes the seat belt retractor according to any one of claims 1 to 9.

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